Safety belt retractor mechanisms which store seat belt webbing in helical wrap are well known. The retractor is often positioned adjacent the occupant seat where seat belt webbing may be drawn from the retractor by the occupant and coupled to other seat belt webbing to form lap and shoulder safety seat belts. To restrain occupants from sudden forward movement during collision, many prior art retractors include an inertia responsive locking device to prevent extraction of the belt. One such retractor mechanism utilizing a lock up device is shown in U.S. Pat. No. 3,858,824 to Stephenson. This lock up device comprises a pendulum supporting an extending arm pivoted at one end to the housing. The opposite end of the arm supports the pawl of a pawl and ratchet gear mechanism in an unlocked position. The pawl is engageable with the teeth of the ratchet gear on a web storage spool to prevent seat belt pay out upon collision. During a collision, the pendulum swings toward the point of impact. This pendular movement lifts the extending arm that in turn pivots the pawl into locking engagement with the ratchet wheel to prevent further pay out of the seat belt.
In view of the substantial loading imparted on the pawl in lock with the ratchet gear during collision, it will be appreciated that the pawl must be rugged. Moreover, since the pawl rotates directly in response to lifting of the arm by the pendulum, the pendulum must have sufficient moment to lift the arm as well as the pawl to lock the pawl and gear assembly. This requires a pendulum of relatively large size and weight to attain the momentum necessary to lock up the retractor mechanism. That requirement increases the overall size and weight of retractors employing such a lock up mechanism. A similar lock up mechanism is shown in U.S. Pat. No. 3,918,658 to Beller.
In accordance with vehicle weight reduction objectives to meet current fuel economy standards, and further in view of vehicle packaging requirements which demand smaller retractors, there exists a need to reduce the size of the above described retractor, without sacrificing reliability, in dual sensitive as well as single sensitive retractor systems.
One object of the present invention, therefore, is to provide a retractor locking mechanism which reduces the overall size and weight of the retractor.
Another object of the invention is to provide a retractor locking mechanism which is rugged in design and capable of reliable operation.
Yet another object is to provide a retractor locking mechanism which can also be used in dual sensitive retractors.